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Accueil > Séminaires > 2017

Band Gaps and Optical Spectra of Halogenated and Hydrogenated Graphenes

Frantisek Karlicky, Ostrava University (République Tchèque)

Salle de séminaire IRSAMC, Jeudi 19 Octobre, 14h - 15h

New two-dimensional materials derived from graphene by attachment of hydrogen and halogens have attracted considerable interest over the past few years because of their potential applications (e.g., in electronic devices) [1]. Here, we consider the effect of electron-electron and electron-hole correlation on the electronic/optical properties of materials under study. Especially, large difference between the experimental optical gap and the electronic band gap from many-body GW theory for fluorographene [2,3] is explained by unusual large binding energies of excitons obtained by solution of Bethe-Salpeter equation (BSE), whereas point defects lower band gaps and absorption energies only slightly [4]. Similar effects are predicted for double-layer fluorographene and graphite fluoride [5]. Moreover, we found huge excitonic effect in recently prepared hydrogenated and fluorinated graphenes, called fluorographanes CFH [6] – the effect is larger than in pure graphane CH or pure fluorographene CF. Finally, we show the importance of careful computational setup for reliable usage of many-body GW and BSE methods.

References
[1] Karlicky F., Datta KKR., Otyepka M., Zboril R., ACS Nano 7 (2013) 6434
[2] Nair RR., Novoselov KS., Geim AK., et al. Small 6 (2010) 2877
[3] Zboril R., Karlicky F., Bourlinos AB., et al., Small 6 (2010) 2885
[4] Karlicky F., Otyepka M., J. Chem. Theory Comput. 9 (2013) 4155
[5] Karlicky F., Otyepka M., Ann. Phys. 526 (2014) 408
[6] Sofer Z., Simek P., Mazanek V., et al., Chem. Commun. 51 (2015) 5633